The present invention concerns an actuator as it is disclosed in WO 99/45631.
Electromagnetic actuation devices, in which a shape memory material (shape memory alloy material) experiences an expansion as a reaction to an applied magnetic field and as a result can then interact with an actuation partner to execute an actuation reaction, are of known prior art. Typically a coil device is thereby assigned to the magnetic shape memory material (MSM=“Magnetic Shape Memory”), which as a reaction to an energisation generates the magnetic field required for the expansion of the shape memory drive element. Since in typical drive element configurations, for example, along a designated axis of expansion of extended bodies, for purposes of triggering the expansion movement a magnetic field input must occur in the body orthogonal to the direction of expansion, a compact build shape can be achieved only with difficulty when implementing suitable modular arrangements or modules, for instance as replacements for common electromagnetic actuators.
While, for instance, the applicant's unpublished German property right application DE 102010 010801 with the deployment of suitable flux-conducting elements for a coil magnetic flux envisages an option in which, in an analogous manner to a conventional cylindrical electromagnetic actuation device, the magnetic coil surrounds the extended drive element coaxially, at least two coil devices are usually deployed for purposes of enabling a magnetic flux input into the drive element; these are typically provided on both sides adjacent to the MSM drive element body.
Such a configuration, presumed to be of known art, then enables, even when deploying standardised flux-conducting modules for the implementation of a magnetic flux circuit, simple and reproducible manufacturing properties for the drive element, although at the same time energetic and volumetric disadvantages arise.
Thus, for instance with the energisation of a first coil device (of a pair of coil devices provided located opposite each other with respect to a central drive element and magnetically connected in series to each other and also to the MSM drive element) sitting on a related core section of a flux-conducting structure, a magnetic flux thereby generated is displaced into an opposing arm and there into the core region of the coil device there provided. The same applies, in the event of the activation of the opposing coil device, for the core region of the first coil device. The end result is that in the case of two activated coil devices a respective effective cross-section of the core region must be dimensioned sufficiently large such that the mutually overlapping fluxes of the two coil devices can be controlled. The disadvantageous consequence of these influences is that the modules of the magnetic circuit must be dimensioned (unnecessarily) large, with resulting disadvantages in dimensions, weights, and costs. In contrast, actuators of small dimensions would definitely bring with them performance disadvantages under these conditions, particularly in terms of undesirable heating and/or prolonged movement and switching times.
With regard to the further prior art reference is made to the article by Rolfs K et al: “Effect of alloying Ni—Mn—Ga with cobalt on thermal and structural properties”, Journal of Physics: Conference Series, Vol. 251, 2010, Pages 012046/1-4 (XP55029781).